Method of feeding wrapping material in a product packaging machine, and a relative feed unit

ABSTRACT

Wrapping material is supplied to the folding stations of a packaging machine, such as a cigarette packer, by a method that includes a step of dividing a continuous strip of multilayer material into single leaves, and a step of feeding the leaves to a wrapping unit; the step of dividing the continuous strip into leaves combines a first stage in which a partial cut is made in the strip by means of a laser device, leaving at least one layer of the multilayer strip intact, and a second stage in which a single leaf is detached by means of a tear device, separating along a score line created by the partial cutting step.

This application claims priority to Italian Patent ApplicationBO2009A000453 filed Jul. 15, 2009, the entirety of which is incorporatedby reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a method of feeding wrapping materialin a product packaging machine, and to a feed unit for implementing sucha method.

Conventional units of the type in question comprise means by which acontinuous strip of paper material is decoiled from a roll, a cutterdevice by which the strip is divided into discrete leaves, and feedmeans by which the single leaves are supplied to a unit or line forwrapping products, such as groups of cigarettes, by way of example.

In conventional feed units, the cutter device generally comprises a pairof counter-rotating rollers equipped with blades, stationed along thepath followed by the continuous strip and placed as close as possible tothe wrapping line.

This type of placement is preferable, in order to avoid transferring theleaves along relatively long feed paths, though not always easilyaccomplished due to the dimensions and general layout of the machine.

Self-evidently, in effect, long transfer distances dictate the use ofhighly complex and costly guidance and inspection systems, needed inorder to ensure that the leaves are handled gently and positionedcorrectly at the moment of initial contact with a relative productdirected onto the wrapping line.

In addition to this drawback, there is the fact that the blades used incutting devices of the aforementioned type require frequent sharpeningand replacement.

It is also a common practice to use multilayer wrapping materials inpackaging machines of the type referred to above.

Materials of this type afford distinctive properties in terms ofstrength, appearance and tightness by virtue of their multilayerconstruction, consisting for example in a layer of paper material and atleast one layer of thermoplastic material.

The object of the present invention is to provide a method of feedingwrapping material in a product packaging machine such as will beunaffected by the drawbacks mentioned above in connection with the priorart, which derive from the enforced positioning of a relatively bulkycutting device in close proximity to the wrapping line of the machine.

A further object of the present invention is to provide a unit capableof implementing the method disclosed.

SUMMARY OF THE INVENTION

The stated objects are duly realized in a method according to theinvention for feeding wrapping material in a product packaging machine,which includes a step of dividing a continuous strip of multilayermaterial into single leaves, and a step of feeding the leaves to awrapping unit; the step of dividing the continuous strip into leavescombines a first stage in which a partial cut is made in the strip bymeans of a laser device, leaving at least one layer of the multilayermaterial intact, and a second stage in which a single leaf is detachedby means of a tear device, separating along a score line created by thepartial cutting step.

The stated objects are realized similarly in a feed unit according tothe invention, comprising a laser device by which weakening lines arescored in the continuous strip at intervals corresponding to the lengthof the single leaves, and a tear device, located in close proximity tothe wrapping unit of the packaging machine, comprising first and secondpairs of rollers rotating substantially tangential one to another, withthe rollers of the second pair driven at a tangential velocity greaterthan that of the rollers of the first pair in such a way as to separatethe single leaves forcibly along the score lines.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail, by way of example, withthe aid of the accompanying drawings, in which:

FIG. 1 is a schematic front view of a unit for feeding wrapping materialaccording to the present invention;

FIG. 2 shows a detail of FIG. 1, enlarged and illustrated in crosssection;

FIG. 3 shows the detail of FIG. 2, viewed in perspective.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, numeral 1 denotes a product packaging machine,for example, a cigarette packer designed to wrap products 2 consistingin groups of cigarettes illustrated schematically as parallelepipedblocks.

The machine 1 comprises a frame 3 of which the front presents a verticalbulkhead 4 and, mounted to the bulkhead, a unit or device 5 by whichwrapping material is fed to a wrapping unit, or wrapping line 6, inreceipt of products 2 advancing along a horizontal conveyor 7.

The feed unit 5 comprises a shaft 8 disposed transversely to thebulkhead 4, carrying a roll 9 from which a continuous strip 10 ofwrapping material is decoiled along a path P established by a pluralityof guide rollers 11 a, 11 b and 11 c, ordered along a feed directionindicated by the arrow denoted F in FIG. 1 and rotatable about axesparallel to the axis of the shaft 8.

The advancing strip 10 is cut partially at a position denoted 12, lyingbetween two of the aforementioned rollers 11 a and 11 b, by a laserdevice illustrated schematically as a block denoted 13.

Located at a further position 14 downstream of the guide roller denoted11 c, along a vertical leg of the feed path P, is a tear device 15 bywhich single leaves 16 are separated from the continuous strip 10 andreleased to the wrapping unit 6, where each one will be wrapped around arespective product 2.

The tear device 15 comprises a first pair of rollers and a second pairof rollers, denoted 17 and 18 respectively. The rollers of each pair 17and 18 rotate substantially tangential one to another, with the rollersof the second pair 18 driven at a tangential velocity greater than thatof the rollers of the first pair 17.

With reference in particular to FIGS. 2 and 3, the strip 10 of wrappingmaterial decoiled from the roll 9 is of multilayer construction,comprising a layer 19 of paper material and a layer 20 of polypropyleneand, sandwiched between the two, a layer 21 of polyethyleneterephthalate.

Polyethylene terephthalate (PET) is a thermoplastic resin especiallysuitable for use in contact with food products, which also has theproperty of being substantially insensitive at least to certainfrequencies utilized by laser cutting devices.

In operation, as the strip 10 passes through the partial cut position12, it is exposed to the action of the laser device 13 at regularintervals, according to the length of the single leaves 16; moreexactly, the laser beam will score a line 22 across the strip, cuttingthrough the layer 19 of paper material and penetrating only as far asthe PET layer.

These score lines 22 made by the laser device serve to weaken the strip10, so that when drawn along a further leg P1 of the feed path P andinto the position denoted 14, it will be separated at the weakened areasby the tear device 15 into a succession of single leaves 16.

Adopting a method and a unit 5 for feeding strip material according tothe invention, in contrast to methods typical of the prior art, thedevice 13 employed to make a partial cut in the strip 10 of wrappingmaterial can be positioned at any convenient distance from the wrappingunit, and the single leaves 16 of material also fed correctly to thewrapping line 6 without the need to install complex guidance andinspection systems.

1) A method of feeding wrapping material in a product packaging machine, including a step of dividing a continuous strip of multilayer material into discrete leaves, and a step of feeding the leaves to a wrapping unit, wherein the step of dividing the continuous strip into leaves combines a first step in which a partial cut is made in the strip by means of a laser device, leaving at least one layer of the multilayer material intact, and a second step in which a single leaf is detached by means of a tear device, separating along a score line created by the partial cutting step. 2) A method as in claim 1, including a step of feeding the continuous strip along a predetermined path subsequent to the partial cutting step and prior to the step of detaching the discrete leaf. 3) A unit for feeding wrapping material in a product packaging machine, operating by the method as in claim 2, wherein the multilayer strip comprises a layer of material substantially insensitive to the cutting frequencies used by the laser device. 4) A feed unit as in claim 3, wherein the tear device comprises a first pair of rollers and a second pair of rollers, the rollers of each pair rotating substantially tangential one to another, and the rollers of the second pair rotating at a tangential velocity greater than that of the rollers of the first pair. 5) A feed unit as in claim 3, wherein the layer of material insensitive to laser frequencies is polyethylene terephthalate (PET). 6) A feed unit as in claim 5, wherein the strip comprises an outer layer of paper material. 